The invention concerns a back-washable filter element which is to be installed in a pressure vessel and has a supporting body of perforated tubes, a central tube, and a head part.
A filter element of this type is known from U.S. Pat. No. 4,473,472. The known filter element which is suitable for residual volume filtration includes a central tube which is closed along its entire length. A filtrate is removed through the central tube and when the filtration is concluded a backwashing agent is fed in opposite the filtration direction for cleaning the filter medium. The central tube is surrounded by perforated tubes to support the filter medium, generally a woven fabric. In the known filter element the filtrate can only be removed via the lower opening of the central tube. This is disadvantageous in that the capacity of the filter is greatly limited by the restricted lumen of the central tube, as is the speed and efficiency of the backwashing.